Purpose of Entrance Slit in Spectrometer: Rgds Evidenso

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    Slit Spectrometer
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Discussion Overview

The discussion centers on the purpose of the entrance slit in a dispersive spectrometer, exploring its role in enhancing resolution, managing diffraction, and its implications for spectrometer design. Participants consider both theoretical and practical aspects of spectrometer functionality.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that the entrance slit creates a single slit diffraction pattern, potentially improving resolution beyond mere beam collimation.
  • Another participant argues that the slit should not be too small to avoid significant diffraction, emphasizing its role in narrowing spectral lines and maintaining spatial coherence.
  • Some participants note that while an entrance slit is not mandatory, it is commonly used in many spectrometer designs for reasons such as improving transmission efficiency and correcting aberrations.
  • It is mentioned that the design of some spectrometers allows for daisy-chaining multiple units to achieve finer spectroscopic detail.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and function of the entrance slit, with some supporting its use for specific advantages while others question its essentiality. The discussion remains unresolved regarding the optimal design considerations for spectrometers.

Contextual Notes

There are limitations in the discussion regarding the assumptions about diffraction effects and the specific design requirements of various spectrometer types. The implications of these factors on performance are not fully explored.

evidenso
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Hi
Can anyone tell me the purpose of a entrance slit in a dispersive spectrometer. What is it good for? I guess it will create a single slit diffraction pattern. Why will this make the resolution better, instead of just colliminate the beam?

Will the slit do some kind of Fourier filtering also?

Rgds
Evidenso
 
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The slit should not be so small that there is notable diffraction from it. Its purpose is simply to make the spectral lines narrow. Consider that even monochromatic light entering a prism at a different spot will be projected at a different spot. So the slit keeps it to one spot.
 
An entrance slit is not a requirement, but it's true that many spectrometer designs (Echelle, use entrance slits.

One reason is overall transmission efficiency and aberration correction- some designs are kinda like imaging systems in that the exit slit is an image of the entrance slit.

Another reason is so that multiple spectrometers can be daisy-chained together to provide ever-finer spectroscopic detail.

Chapter 8 of the Richardson Grating Handbook has addtionial details:

http://gratings.newport.com/handbook/handbook.asp
 
Last edited by a moderator:
Andy Resnick said:
An entrance slit is not a requirement, but it's true that many spectrometer designs (Echelle, use entrance slits.

One reason is overall transmission efficiency and aberration correction- some designs are kinda like imaging systems in that the exit slit is an image of the entrance slit.

Another reason is so that multiple spectrometers can be daisy-chained together to provide ever-finer spectroscopic detail.

Chapter 8 of the Richardson Grating Handbook has addtionial details:

http://gratings.newport.com/handbook/handbook.asp


Hi
Thanks, very helpful.
 
Last edited by a moderator:

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